FIG. 13a is a schematic perspective view of an example of a shield structure (see, for example, Patent Document 1). FIG. 13b is a schematic exploded view of the shield structure shown in FIG. 13a. The shield structure 40 includes a shield cover 42 that covers a section to be shielded Z on a circuit board surface of a circuit board 41 so as to shield an electric circuit formed in the section to be shielded Z on the circuit board 41. The shield structure 40 has a plurality of shield-cover attachment bases 43 arranged along the periphery of the section to be shielded Z with intervals therebetween on the board surface of the circuit board 41. The shield cover 42 includes a cover plate 44 that covers the section to be shielded Z on the circuit board 41 and a peripheral wall 45 that extends from the periphery of the cover plate 44 toward the periphery of the section to be shielded Z. The peripheral wall 45 of the shield cover 42 has attachment tabs 46 disposed along the edge thereof at positions corresponding to the positions where the shield-cover attachment bases 43 are arranged.
As shown in FIG. 13c, each shield-cover attachment base 43 is constituted of a rectangular parallelepiped box, and has an opening 47 in the top surface thereof. The opening 47 has edge portions that face each other, and a pair of spring terminals 48A and 48B extend from the edge portions toward the inside of the shield-cover attachment base 43. The pair of spring terminals 48A and 48B are arranged to be pressed against each other. The shield-cover attachment bases 43, each of which has the above-described structure, are arranged on the circuit board 41 such that the bottom surfaces of the shield-cover attachment bases 43 are in contact with the board surface of the circuit board 41. When the shield-cover attachment bases 43 are arranged on the circuit board 41 in the above-described manner, the spring terminals 48A and 48B are connected to the ground of the circuit board 41 via ground connection means (not shown).
The shield cover 42 is attached to the circuit board 41 such that each attachment tab 46 is inserted between the spring terminals 48A and 48B of the corresponding shield-cover attachment base 43 and is elastically held between the spring terminals 48A and 48B, as shown in FIG. 13d. The shield cover 42 is connected to the ground of the circuit board 41 so as to shield the section to be shielded Z on the circuit board 41. In FIG. 13b, the reference numeral 50 denotes components included in the electric circuit.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-4093
In the process of arranging components including the shield-cover attachment bases 43 on the board surface of the circuit board 41, the components may be conveyed to the circuit board 41 in the following manner. That is, a conveying suction nozzle retains the top surface of a component by suction and conveys the component to a predetermined arrangement position on the circuit board 41. The suction conveying method is often used because the conveying device has a simple structure and the rate of failure in the process of conveying the component is low.
However, the conveying suction nozzle cannot retain the top surface of the shield-cover attachment bases 43 top surfaces thereof by suction because each of the shield-cover attachment bases 43 in the shield structure 40 has the opening 47 in the top surface thereof. Therefore, the shield-cover attachment bases 43 cannot be conveyed by the suction conveying method, and another conveying method must be used. As a result, an expensive conveying device having a complex structure, for example, is required. This causes a problem that the manufacturing costs will be increased.
In addition, the shield-cover attachment bases 43 must be placed on the circuit board 41 such that the surfaces in which the spring terminals 48A and 48B are formed face upward. In other words, the shield-cover attachment bases 43 must be carried and arranged while the orientation of the shield-cover attachment bases 43 in the vertical direction is controlled. Therefore, a cumbersome process is required in which, for example, the orientations of the shield-cover attachment bases 43 to be conveyed are adjusted in the vertical direction before the shield-cover attachment bases 43 are conveyed to the circuit board 41. This preparation process may require additional tools or materials, and the number of manufacturing steps is increased. As a result, high costs are incurred.